Fixture for generating involutes



Sept. 29, 1953 J. SILVAGI 2,653,426

FIXTURE FOR GENERATING INVOLUTES Filed May 1. 1952 2 Sheets-Sheet l IMI r 1 JNVENTOR. L CIOSiP/l .S/L VA 6/ BY W W ATTORNEY Sgpt. 29, 1953 J. SILVAGI 2,

FIXTURE FOR GENERATING INVOLUTES Filed May 1, 1952 2 Sheets-Sheet 2 m- E i as 20 /9 2o 25' i /3 INVENTOR. Jon-P0 3/41/46/ BYaQMM W ATTORNEY Patented Sept. 29, 1953 UNITED STATES PATENT OFFICE 2,653,426 GENERATING mvoturiis 'Josirh Silvagi, Detroit,'Mich. 'iApplicationMay'l, 1952, Serial N0.'285,489 "11 claims. ((151-232) This invention relates to production machinery, and has particular reference to a device for holding work pieces upon which it is desired to form an involute curve, such as upon the teeth on a f xed beam, which base cylinder supports I the work piece and using either a fiat plane or a conical surface of a grinding wheel to form the involute curve on thework piece. a I

noth ob c of th nve t n s tq v d a device of the character indicated, with which gears of agreat variety of sizes may be worked upon by the simple expedient of changing the base c l a .v d x at s.-- Another object of theinvention is toproyide a device of the character indicated which may b iliz a a e pq 'ma h a 9. m be combined with another machine for moreextended operations. For example, a conventional surface grinder may be'converted into a gear grinder by utilizing this'device on a magnetic Another object of the invention is to provide a deviceof the character indicated, with which conical involute gears'may be formed by setting the base of 'the device ina tilt angle. I a

The foregoing and other objects and advantages of the invention will become more apparent as the description proceeds, reference being made rmm um totimeto the accompanying drawing forming partof the within'disclosure, in which drawmgi r Fig. l' is aside elevational view, with parts broken away, of a device embodying the invention.

Fig. 2 is a section taken on the line 2-2 of i .1, "Referring now more pa 'ly' to the drawing,it' will be understood'that in the embodiment herein disclosed the reference character 1 indicates a base plate, the reference 'character 8 "indicates 'a'to'p or cover 'm'emberfand the refer- '50 ence'c'haracters "9, "I0, and ill indicate Support- 'andisupportthe moving parts oflthe device. The

gether by any suitable means, such as machine screws [2 or the like, the heads of which are preferably countersunk to provide flush surfaces at top and bottom. a t

A vertically adjustable platform 13 is supported on a screw jack [4, the ;base 15 of which rests on the base member 1. The screw jack ii 4 is raised and lowered by means of the nut 116, all of which is conventional. The platfcrm I3 is further supported by means of threaded rods or bolts I! which extendthrough threaded bores [8 formed at each end of the platform [3. The lower ends of the threaded rods er' bolts llride 0n the base member I, whereby, upon rotation of the threaded rods or bo1ts"I1 the platform i3 may be raised and'lowered., Positioned on top of the platform l3 and adapted to move longitudinally thereon, is a carriage-like member which consists of arectangularplate 1 9, having cut out portions 20 at either corner for the accommodation of the ball bearing rollers 21, 2 2, 23, and 25, which are adapted to rotate on suitable pins 25, which are-;press fitted into bores. formed in the plate 19. A I

Positioned on ,top of the rollers 21,22, .23, and

'24 and rotatable therewithis a base circle member 26, which is in the form Of'ia solid cylinder having .a bore 27 therein, in which is press ,fiftted a hollow shaft 28, in which hollow shaft 28 is slip fitted a solid shaft 29. The base circle member 26 is :locked on the hollow shaft 28 byinea'nsv of a set screw which engages a threadedlboretfi. The base circle 26 is provided with a peripheral rib 3!, which engages a slot tjformed'inthetbp frame member-8, which serves to prev nt axial movement of the base circle member '26 before pressure is applied thereon as hereinafter Idescribed.

The upper frame member 8 has 'formed on its under side; as at 33, a plurality of serrations, which serrations are approximately .020 inch apart and formedwith double ngles .oflapproximately f Thebase circle member 26 is preferably made of softer metal than the up er frame member 8, so that when pressure 'is applied against the base circle'm'emb'erfi, and thelatter is f rst rolled against'the upper .fraihemember 8, the serrations 33iareimparted .to the'p'eripm ery of the base circle member 26,750 that there can be no'slippage of'themember '25 asitriiolls against the under side of the member .8. This 'is an important featurei'of the invention,

The hollow sh'aft28 is provided with an en- 'larged portion "28A on whichisisecured by meanspf a "set "screw' 34 "an" indexing arm es.

which arm 35 has an outwardly extending portion 36, the latter having a vertical bore 31 in which is mounted an indexing plunger 38. The plunger 38 is adapted to be movable in the bore 31 either by threading the same or by spring loading the plunger 38, so that it may be lifted against the spring load.

The central shaft 29 has mounted on it an indexing plate 39 which has indexing slots 40 equally spaced about its periphery, which indexing slots 40 are equal in number and are spaced to conform to the spacing of the teeth 4| on the gear work piece 42, which is mounted on the opposite end of the central shaft 29. The index plate 39 is held on the shaft 29 by means of 'a' washer 43 and the machine screw 44. The ref-.

erence character 45 indicates a grinding wheel I mounted on the shaft 46, which grinding wheel is dressed to impart the proper curvature to the,

teeth 4| of the work piece 42. The work piece 42 is preferably held on the end of the shaft 29 by means of a machine screw 47, and the shaft 29 is held against axial thrust by means of a collar 48, which is secured thereto by means of a set screw 49.

In using the device, the proper base circle member 26 and the proper index plate 39, for the grinding of the work piece 42, are mounted and positioned as hereinabove described. Pressure is then exerted on the platform i3 by means of the threaded jack l4 and the threaded rods l1. The arm 35 is then rocked back and forth .on its pivot, causing a rotating motion to be imparted to the index plate 39, the hollow shaft 28, the solid shaft 29, and the base circle 25, as well ,as the work piece 42. This causes the base circle 123 to roll against the serrations 33 formed on the under side of the frame member 8, whereby the frame serrations are imparted to the periphery of the base circle 23, so that thereafter there can be no slippage between the members 3 and 2E. The rotation of the base circle 23, because of its supporting contact with the rollers 29, 22, 23, and 24, causes the carriage 19 to move in the direction of rotation of the base circle 23, which also causes a lateral movement of the base circle 25 and the carriage 19. This rotating and lateral movement of the base circle 26 generates an involute curve on the teeth 4| of the work piece 42 when the grinding wheel 45 is brought into contact therewith.

In the generation of an involute helicoid, the fixture is positioned on a surface grinder (not shown) having a reciprocable table. The axis of the cylindrical member 25 and simultaneously the workpiece 4!, 42 is set at an angle with the surface grinders reciprocal motion. As the cylindrical member 25 rolls along its circumference with non-slip contact against the serrated frame member 8, the wheel path generates a true helix on the workpiece 4!, 42, The wheel axis re' mains perpendicular to the grinders reciprocating motion. The shape of the wheel may be saucer shaped or trapezoidal in cross-section. Since the involute helicoid is a developable helicoid, it may be generated by a succession of straight line cuts moved along a helix. Thus, during generation of the helix on the work cylinder, an involute tooth is simultaneously generated. The straight line cuts will lie tangent to the base cylinder of the gear being formed.

Having described my invention, what I claim and desire to secure by Letters Patent is:

1. In a device of the character described in combination, a rectangular frame supporting a.

4 top plate provided with serrations on its under surface, a vertically movable platform positioned below said top plate, a carriage longitudinally shiftable on said platform, rollers on said carriage, a cylindrical member supported on the rollers of said carriage and arranged for rotation thereon and longitudinal travel therewith and further arranged for rolling contact with said top plate, a hollow shaft in said cylindrical memher and rotatable therewith, a solid shaft rotatable in said hollow shaft, an indexing arm secured to said hollow shaft and movable therewith, an indexing plate secured to one end of said solid shaft and movable therewith, a plunger reciprocablev in an extension of said indexing arm and having an end arranged to engage indexing slots formed on the periphery of said indexing plate whereby to rotate said plate, and

means for supporting a work piece at the other end of said solid shaft.

2. The structure defined in claim 1, there being threaded openings in said top plate and said platform and threaded rods therein, for adjusting the vertical movement of said platform.

3. The structure defined in claim 1, in which said rectangular frame has open spaces at the sides thereof through which are extended the ends of said hollow shaft and said solid shaft.

4. The structure defined in claim 1, in which the length of the carriage is less than the diameter of said cylindrical member.

5. In a device of the character described in combination, a base plate, a top plate, corner posts for supporting said top plate, a vertically shiftable platform positioned below said top plate, a screw jack supported on said base plate and arranged to support said platform, threaded rods extending through openings in said top plate and threaded bores formed in said vertically shiftable platform, a carriage having wheels arranged to roll longitudinally on said platform, a cylindrical member supported on the wheels of said carriage for rotation and transverse movement therewith and arranged for rolling contact with said top plate, a hollow shaft extending through said cylindrical member and rotatable therewith, a solid shaft rotatable within said hollow shaft, an indexing plate secured to one end of said solid shaft, the other end of said Shaft b in rr n d to supp rt a Work piece, and an indexing arm secured to an extension of said hollow shaft, said indexing arm having a plunger shiftable therein, one end of said plunger being arranged to engage driving eleniertits formed on the periphery of said indexing D a e.

6. The structure defined in claim 5, includin uniformly spaced serrations formed on the under surface of said top plate and arranged to contact the periphery of said cylindrical member.

7. The structure defined in claim 5, in which said cylindrical member has a concentric peripheral rib arranged to engage an arcuate slot formed on the under side of said top plate member.

8. In a device of the character described in combination, a base plate, a top plate, corner posts for supporting said top plate on said base plate, a, rectangular platform mounted for vertical adjustment on said base plate, a, carriage having wheels arranged to roll on the upper surface of said platform, a cylindrical member having a diameter reater than the length of said 'P lllage, said cylindrical member being i 11.. ing contact with said top plate and being arranged to travel with said carriage and rotate with the Wheels thereof, a hollow shaft concentrically mounted in said cylindrical member and extending beyond the sides of said corner post members, means for locking said cylindrical memher to said hollow shaft, a solid shaft rotatable in said hollow shaft and extending beyond the ends thereof, a driving plate having peripheral indexing means thereon, secured to one end of said solid shaft, the other end of said solid shaft being arranged to support a work piece having teeth corresponding to said peripheral driving means, an enlarged section on said hollow shaft, an indexing arm secured to said hollow shaft extension, said arm having an outwardly extending portion, and a plunger in said arm extension, said plunger having an end adapted to engage the driving elements formed on the periphery of said indexing plate.

9. The structure defined in claim 8, including uniformly spaced serrations formed on the under face of said top plate member and arranged to contact the periphery of said cylindrical member.

10. The structure defined in claim 8, including threaded rods supported by said top plate member, and extending through threaded bores formed in said vertically shiftable platform.

11. The structure defined in claim 8, in which said cylindrical member has a peripheral rib arranged to engage an arcuate slot formed on the under face of said top plate member.

JOSEPH SILVAGI.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,942,416 Fellows Jan. 9, 1934 1,961,663 Goulder June 5, 1934 

